In the field of stereoscopic (3D) image display apparatus, there has been an increasing demand for λ/4 plate which functions to convert linearly polarized light of a specific wavelength into circularly polarized light.
Among several known systems of stereoscopic image display apparatus, one known system is such as allowing the viewer, who wears glasses with a liquid crystal shutter function for viewing stereoscopic images, to recognize two-dimensional images as stereoscopic (three-dimensional: 3D) images. One promising system at present is such as displaying right-eye images and left-eye images, as parallax images, on a display screen, while sequentially and alternately switching them, and allowing the viewer who wears the glasses for viewing stereoscopic images to view the images on the liquid crystal display (see Patent Document 1, for example).
This sort of stereoscopic image display apparatus, configured by the liquid crystal display and the glasses for viewing stereoscopic images, however, suffers from seeing double (also referred to as crosstalk) due to lowered luminance or hue changes, when the viewer tilts the head. The λ/4 plate is effectively used on the viewing side of the liquid crystal display, for the purpose of suppressing decrease in the luminance and hue changes when the head is tilted.
More recently, there has been a growing need of organic electroluminescence (also referred to as organic EL) image display apparatus characterized by lower power consumption and small-sized surface emission element, and this consequently increases a need for organic EL image display apparatus with a function for displaying stereoscopic images.
The organic EL image display apparatus needs a circularly polarizing plate with a λ/4 plate incorporated therein, in order to avoid hue degradation due to reflected light from a metal electrode. Accordingly, the circularly polarizing plate of this invention uses a λ/4 plate (referred to as “λ/4 plate T2”, hereinafter) on the luminescent layer side in order to block reflection on the metal electrode of the organic EL image display apparatus, and a λ/4 plate (referred to as “λ/4 plate T1”, hereinafter) on the viewer's side in order to prevent the crosstalk in the stereoscopic images (also referred to as 3D images).
For the purpose of completely blocking the reflected light in the visible light range on the organic EL image display apparatus, it is now necessary to establish λ/4 phase difference over the entire wavelength of visible light. However, improvement in the wavelength dispersion of the phase difference is basically in a trade-off relation with the phase difference per se, and is difficult. In some wavelength range, the reflected light is blocked only with difficulty, wherein the reflected light in the red region, where the luminous efficiency is high, will degrade visibility. This has, however, not understood as a serious problem in the visibility for the general EL image display apparatuses, so long as the reflected light in the red region, where the luminous efficiency is high, is successfully blocked by setting a relatively large level of phase difference of the λ/4 plate.
The organic EL image display apparatus imparted with the 3D image function was, however, found to cause crosstalk in the 3D image, due to reflected light in the blue region which could not be blocked by the circularly polarizing plate.
On the other hand, Patent Document 2 and Patent Document 3 disclose the organic EL display apparatuses and circularly polarizing plates provided with a cellulose ester film, while making no description on possibility of imparting the 3D image function or any associated problems mentioned above.